The present invention, in some embodiments thereof, relates to novel aquaporin polynucleotides and polypeptides, and more particularly, but not exclusively, to methods of using same for increasing abiotic stress tolerance, water use efficiency (WUE), fertilizer use efficiency (FUE), biomass, vigor and/or yield of a plant.
Abiotic stress conditions such as salinity, drought, flood, suboptimal temperature and toxic chemical pollution, cause substantial damage to agricultural plants. Most plants have evolved strategies to protect themselves against these conditions. However, if the severity and duration of the stress conditions are too great, the effects on plant development, growth and yield of most crop plants are profound. Furthermore, most of the crop plants are highly susceptible to abiotic stress (ABS) and thus necessitate optimal growth conditions for commercial crop yields. Continuous exposure to stress causes major alterations in the plant metabolism which ultimately leads to cell death and consequently yield losses.
The global shortage of water supply is one of the most severe agricultural problems affecting plant growth and crop yield and efforts are made to mitigate the harmful effects of desertification and salinization of the world's arable land. Thus, Agbiotech companies attempt to create new crop varieties which are tolerant to different abiotic stresses focusing mainly in developing new varieties that can tolerate water shortage for longer periods.
Studies have shown that plant adaptations to adverse environmental conditions are complex genetic traits with polygenic nature. When water supply is limited, the plant WUE is critical for the survival and yield of crop. Since water scarcity is increasing and water quality is reducing worldwide it is important to increase water productivity and plant WUE. Many of the environmental abiotic stresses, such as drought, low temperature or high salt, decrease root hydraulic conductance, affect plant growth and decrease crop productivity.
Genetic improvement of FUE in plants can be generated either via traditional breeding or via genetic engineering. Attempts to improve FUE in transgenic plants are described in U.S. Patent Applications 20020046419 to Choo, et al.; U.S. Pat. Appl. 20030233670 to Edgerton et al.; U.S. Pat. Appl. 20060179511 to Chomet et al.; Yanagisawa et al. [Proc. Natl. Acad. Sci. U.S.A. 2004, 101(20):7833-8]; Good A G et al. [Trends Plant Sci. 2004, 9(12):597-605]; and U.S. Pat. No. 6,084,153 to Good et al.
Aquaporins (AQPs), the water channel proteins, are involved in transport of water through the membranes, maintenance of cell water balance and homeostasis under changing environmental and developmental conditions [Maurel C. Plant aquaporins: Novel functions and regulation properties. FEBS Lett. 2007, 581(12):2227-36]. These proteins are considered to be the main passage enabling transport of water and small neutral solutes such as urea and CO2 through the membrane [Maurel C. Plant aquaporins: Novel functions and regulation properties. FEBS Lett. 2007 Jun. 12; 581(12):2227-36]. In plants, AQPs are present as four subfamilies of intrinsic proteins: plasma membrane (PIP), tonoplast (TIP), small and basic (SIP) and NOD26-like (NIP). The total number of AQP members in plants, as compared to animals, appears to be surprisingly high [Maurel C., 2007 (Supra)]. For instance, 35 AQP genes have been identified in the Arabidopsis genome [Quigley F, et al., “From genome to function: the Arabidopsis aquaporins”. Genome Biol. 2002, 3(1):RESEARCH0001.1-1.17], 36 in maize [Chaumont F, et al., 2001, “Aquaporins constitute a large and highly divergent protein family in maize. Plant Physiol”, 125(3):1206-15], and 33 in rice [Sakurai, J., et a., 2005, Identification of 33 rice aquaporin genes and analysis of their expression and function. Plant Cell Physiol. 46, 1568-1577]. The high number of AQPs in plants suggests a diverse role and differential regulation under variable environmental conditions [Maurel C., 2007 (Supra)].
WO2004/104162 to the present inventors teaches polynucleotide sequences and methods of utilizing same for increasing the tolerance of a plant to abiotic stresses and/or increasing the biomass of a plant.
WO2007/020638 to the present inventors teaches polynucleotide sequences and methods of utilizing same for increasing the tolerance of a plant to abiotic stresses and/or increasing the biomass, vigor and/or yield of a plant.
Lian H L, et al., 2006 (Cell Res. 16: 651-60) over-expressed members of the PIP1 subgroup of AQPs in rice. Aharon R., et al. 2003 (Plant Cell, 15: 439-47) over-expressed the Arabidopsis plasma membrane aquaporin, PIP1b, in transgenic tobacco plants.